[tip: x86/entry] x86/debug: Remove handle_debug(.user) argument

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the x86/entry branch of tip:

Commit-ID:     7043679a989af969e9f20cc7d90195b36f54036f
Gitweb:        https://git.kernel.org/tip/7043679a989af969e9f20cc7d90195b36f54036f
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Wed, 02 Sep 2020 15:25:54 +02:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Fri, 04 Sep 2020 15:12:52 +02:00

x86/debug: Remove handle_debug(.user) argument

The handle_debug(.user) argument is used to terminate the #DB handler early
for the INT1-from-kernel case, since the kernel doesn't use INT1.

Remove the argument and handle this explicitly in #DB-from-kernel.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Acked-by: Andy Lutomirski <luto@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200902133200.907020598@xxxxxxxxxxxxx

---
 arch/x86/kernel/traps.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 9cb39d3..58bc434 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -783,25 +783,18 @@ static __always_inline unsigned long debug_read_clear_dr6(void)
  *
  * May run on IST stack.
  */
-static void handle_debug(struct pt_regs *regs, unsigned long dr6, bool user)
+static void handle_debug(struct pt_regs *regs, unsigned long dr6)
 {
 	struct task_struct *tsk = current;
 	bool user_icebp;
 	int si_code;
 
 	/*
-	 * If DR6 is zero, no point in trying to handle it. The kernel is
-	 * not using INT1.
-	 */
-	if (!user && !dr6)
-		return;
-
-	/*
 	 * If dr6 has no reason to give us about the origin of this trap,
 	 * then it's very likely the result of an icebp/int01 trap.
 	 * User wants a sigtrap for that.
 	 */
-	user_icebp = user && !dr6;
+	user_icebp = !dr6;
 
 	/* Store the virtualized DR6 value */
 	tsk->thread.debugreg6 = dr6;
@@ -874,7 +867,13 @@ static __always_inline void exc_debug_kernel(struct pt_regs *regs,
 	if (kprobe_debug_handler(regs))
 		goto out;
 
-	handle_debug(regs, dr6, false);
+	/*
+	 * The kernel doesn't use INT1
+	 */
+	if (!dr6)
+		goto out;
+
+	handle_debug(regs, dr6);
 
 out:
 	instrumentation_end();
@@ -904,7 +903,7 @@ static __always_inline void exc_debug_user(struct pt_regs *regs,
 	irqentry_enter_from_user_mode(regs);
 	instrumentation_begin();
 
-	handle_debug(regs, dr6, true);
+	handle_debug(regs, dr6);
 
 	instrumentation_end();
 	irqentry_exit_to_user_mode(regs);